For the past 25 years, people suffering from depression have been treated with antidepressant drugs like Zoloft, Prozac and Paxil — three of the world’s best-selling selective serotonin reuptake inhibitors, or SSRIs. But people are questioning whether these drugs are the appropriate treatment for depression, and if they could even be causing harm.

The drugs are designed to address a chemical imbalance in the brain and thereby relieve the symptoms of depression. In this case, it’s a shortage of serotonin that antidepressants work to correct.

In fact, there are pharmaceutical treatments targeting chemical imbalances for just about every form of mental illness, from schizophrenia to ADHD, and a raft of anxiety disorders. Hundreds of millions of prescriptions are written for antipsychotic, antidepressant and anti-anxiety medications every year in the United States alone, producing billions of dollars in revenue for pharmaceutical companies.

Robert Whitaker has won numerous awards as a journalist covering medicine and science, including the George Polk Award for Medical Writing and a National Association for Science Writers’ Award for best magazine article. (Courtesy Robert Whitaker)

But what if the very premise behind these drugs is flawed? What if mental illnesses like depression aren’t really caused by chemical imbalances, and that millions of the people who are prescribed those drugs derive no benefit from them? And what if those drugs could actually make their mental illness worse and more intractable over the long term?

Investigative journalist Robert Whitaker argued that psychiatric drugs are a largely ineffective way of treating mental illness in his 2010 book called Anatomy of an Epidemic: Magic Bullets, Psychiatric Drugs and the Astonishing Rise of Mental Illness in America.

Whitaker maintains that the foundation of modern psychiatry, the chemical imbalance model, is scientifically unproven.

“If you dig into the science behind it,” Whitaker told Michael Enright, host of The Sunday Edition on CBC Radio, “you’ll find out that it’s not true, and that this was a hypothesis that arose in the 1960s, that depression was due to low serotonin, and that it was investigated and found not to be true by the early 1980s. And there was subsequent research to see if this was so, and it never panned out.

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“And as early as 1998, the American Psychiatric Association in its textbook says we’re not finding that people with depression have any abnormality in their serotonin, but because it’s such an effective metaphor for getting people to take the drugs and sell the drugs, it’s continued to be promoted.”

Whitaker’s book was unsurprisingly controversial upon its release, but it went on to win the 2010 Investigative Reporters and Editors Book Award. And since its publication, an increasing number of influential psychiatric researchers have publicly come around to Whitaker's point of view.

​In fact, Ronald Pies, a psychiatrist and the former editor of The Psychiatric Times, refers to the chemical imbalance hypothesis as an “urban legend” that well-informed psychiatrists never bought into.

Whitaker says that when Anatomy of an Epidemic came out, the controversy wasn’t so much over his debunking of the chemical imbalance hypothesis. It was over his finding that people who took psychiatric drugs were more likely to exhibit symptoms five years after being diagnosed than those who did not take the drugs.

But Thomas Insel, the director of the National Institute of Mental Health in the U.S., has weighed in on antipsychotic drugs, used to treat mental illnesses like schizophrenia, and reached a conclusion that echoes Whitaker’s.

According to Whitaker, research suggests that while people suffering from depression may not have low serotonin levels to begin with, the use of SSRIs reduces the brain’s capacity to produce serotonin on its own, leading to a worsening of symptoms when patients stop taking the drugs.

“One of the worries,” said Whitaker, “is that if you’re on these medications long enough, when you come off, will your brain re-normalize? And that’s an open question now.

“What is quite clear is that the drug alone rarely leads to long-term recovery.”

[You can listen to Michael Enright’s full interview with Robert Whitaker this weekend on The Sunday Edition, just after the 9 a.m. news on CBC Radio One, or in the player at the top-left of this story.]

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